Junction connections of the type mentioned in the introduction are used for connection between all kinds of torque-transmitting components and the shafts belonging to them. As an example, but by no means exclusively, junctions of this class are used to connect torque levers or control arms to shafts or stabilizer means. One of the fields of use here is in the area of the shock- and vibration-absorbing suspension of motor vehicle driver's cabs, especially in trucks and similar heavy-duty trucks, in order to uncouple the driver's cab from the chassis of the vehicle in respect to vibrations and motions.
Since the spring rates of the chassis springs are inevitably high in heavy-duty trucks because of the heavy vehicle loads, unevennesses in the road surface or even vibrations from axles and the drivetrain are still transmitted to a considerable extent to the chassis via the axle spring mounting. In order to minimize the transmission of such continuous shocks and vibrations to the driver's cab and hence to the driver's workplace in terms of ergonomics and occupational safety, driver's cab suspensions have been developed in which the driver's cab is supported on the vehicle chassis with the use of a separate suspension system. Such suspension systems for the driver's cab can be designed with lower spring rates and softer shock absorbers than the axle suspension thanks to the much lower weight of the driver's cab compared to the weight of the vehicle, and unevennesses of the road surface or vibrations originating from the drivetrain or axles of the vehicle can therefore be isolated or kept away markedly better from the driver's workplace thanks to such cab suspension systems.
Such suspension means for driver's cabs are of a complicated design, especially in case of increased requirements on the supporting of lateral forces or kinematics, for example, the suppression of pitch and roll. Thus, besides the spring and absorber elements, roll stabilizers must be provided, similarly to the case of axle suspensions of motor vehicles, with which roll stabilizers the undesired, lateral roll of the driver's cab relative to the chassis of the vehicle can be limited.
Roll stabilizers in the form of torque rods or stabilizer shafts, by which the spring compression paths of the suspension elements of the driver's cab, which elements are the left and right elements relative to the direction of travel, are coupled to a certain extent, are used for roll stabilization—for example, during travel on an oblique road surface or in curves, but also, e.g., in the case of unevennesses on one side of the road surface—in suspension means for driver's cabs according to the state of the art.
Torque levers, whose respective end located away from the shaft is connected to the driver's cab by means of a bearing, while the end of the torque levers that is located close to the shaft has a connection to the roll stabilizer, are arranged here, in general, at the two axial ends of the roll stabilizer to introduce the forces, torques and motions of the driver's cab into the roll stabilizer. The bearing of the torque levers that is rigidly connected to the chassis is represented here either by the roll stabilizer itself, or another mounting point each, which is used for connecting the torque levers to the chassis and for introducing the forces of reaction occurring during rolling motions into the chassis, is arranged at the end of the torque levers that is the end close to the shaft.
However, junction connections of this class especially between roll stabilizers and the torque levers belonging to them are subject to high stresses during their lifetime. This is especially true when, for example, for reasons of weight reduction while increasing the torsional rigidity at the same time, torque rods or stabilizer shafts for roll stabilizers are designed in the form of comparatively thin-walled torsion tubes or hollow shafts.
It is known from the state of the art in connection with the torque-transmitting transmission of such torsion tubes to corresponding junction components, for example, torque levers, that the torque levers with the torsion tubes are especially welded or pressed together with the torsion tubes. However, a connection established in this manner between the torque lever and the torsion tube represents a heavily loaded potential weak point in both cases.
In case of a welded connection between the torque lever and the torsion tube, this is linked above all with the heat introduced during welding and with the microstructural changes associated therewith as well as with notch stresses. Even though pure pressed connections can be established between the torsion tube and the torque lever by comparatively gentle cold forming, they often fail to attain the necessary service life in the case of the strong forces and high torques that occur. This is also true when a cross-sectional shape that differs from the circular shape is selected in the area of the connection to the junction component for the purpose of increasing the torque that can be transmitted.
This is linked, especially in the comparatively thin-walled torsion tubes used for weight reasons, with the fact that the tube wall can transmit only limited pressing and shearing forces into the torsion tube in the area in which the force is introduced. For example, force fits between the hollow shaft and the junction component cannot be designed with the rigid press fit required for transmitting high torques for this reason. When the comparatively weak specific forces that can be transmitted are exceeded, the tube wall will therefore separate in the area of the press fit of the torque lever, or the tube wall can be pressed in, which leads to the subsequent failure of the tube cross section.
However, as the applicant found out, the field of application of the junction connection also extends, for example, to roll stabilization and axle guiding especially in utility vehicle axles. Mainly roll stabilizers consisting of solid material and bent from one piece, which have a correspondingly heavy weight, especially in heavy utility vehicles, and whose degree of material utilization is conceivably unfavorable in respect to the intended twisting and torsional rigidity, are used for the roll stabilization of utility vehicle axles in the state of the art. The replacement of the massive roll stabilizers with bulky, comparatively thin-walled and hence lighter-weight hollow shafts has hitherto often been unsuccessful because of the problematic connection technique between such hollow shafts and the torque-transmitting junction components, for example, torque levers.